Heater having means to recirculate partially cooled products of combustion



Aug. .1, 1950 H. J. DE N. MCCQLLUM 2,51?,399

. HEATER HAVING MEANS To RECIRCULATE PARTIALLY cooLED PRODUCTS oF coMBusTloN Filed March 23, 1945 2 Sheets-Sheet l Aug. l, 1950 H. J. DE N. MccoLLuM 2,517,399

HEATER HAVING MEANS TO RECIIRCULTEV PARTIALLY COOLED PRODUCTS 0F COMBUSTIN Filed March 25, 1945 2 Sheets-Sham, 2

Patented Aug. 1, -1950 HEATER HAVING MEANS To RELCIRCULATE `PiurrIALlm COOLEn PRODUCTS F COM- BUSTIDN .Henry J. De N, Mcoilum, deceased, late yof 011i-,

cago, Ill., by Thelma McCollum, executrix, Ghicago, Ill., assigner to Stewart-Warner Corporation, Chicago, Ill., a corporationkof Virginia n Application Mar-0h23, 194'5, Serial No. 584,360

' The invention relates generally to heaters and more particularly to `heaters "of the sealed combustion type, adapted for use .in aircraft.

In heaters vwhich ,burn mixtures of liquidhydrocarbon fuels and air, difficulty is occasionally experienced :in maintaining combustion. .Due to temporary interruptions or reductions in the pressure of the mixture supplied, the flame may become extinguished. It has also beenfound that if someof the exhaust gases of a heater are .mixed with the burning fuel-air mixture,v combustion vof the fuel is more complete and the flame will be blue.

It is therefore an object of my invention to providean improved sealedcombustion type heater having means for mixing a certain proportion of the exhaust gases with the burning fuel-air mixture.

A further .object is to provide .a sealed combustion type heater in which improved combustion is obtained by mixing exhaust gases with the burning fuel mixture in the combustion chamber, thereby reducing the temperature of the exhaust gases.

A further object .is to `'provide an improved Asealed combustion type .heater which is :simple in construction, efcient in operation and may be economically manufactured.

Otherlobjects and advantages will appear yfrom :the following description, .reference beinghad to the accompanying drawings, in which Fig. 1 is a view of one form of the invention; and

Fig. 2 is a similar view of a modification of the invention.

In the form of invention shown in Fig. l, there is provided a casing 4t having an inlet shroud 42 and an outlet shroud 44. At the inlet end of the casing 42, there is located a motor drivenfan 46 for causing flow of Ventilating air through the casing. A shell S, provided with heat exchange ns 50, is suitably mounted within the casing 40 and has a stamped cup 52 suitably secured thereto, this cup 52 forming a combustion chamber 54. An annular flange baille 56 is secured Within the cup 52. The mixture of fuel and air is supplied through a pipe 58 which is located between the baffle 56 and the end wall of the cup 52, the end portion of this pipe extending along the inner wall of the cup 52 so as to introduce the combustible mixture tangentially and thus impart a rotary swirling motion to the air and fuel mixture as it enters the combustion chamber 54.

An ignter 60 is located in a suitable housing 2 claims. (c1. 12s- 116) member forming a ,chamber which communicates with the combustion chamber through a pair of openings @6l and y52 in rthe 'manner moreffully shown in applicants` 4Patent ,No 2,.-eil704. combustible `mixture enters the ignter through the port ,6 l and the ignited hows into the combustion chamber through :the port t2. The products of combustion .aredexhausted ,from the v48 throughlan exhaust fcondnitiil.: Within this shellil is :a return tube 65 .suitably supported by 'brackets L65, ,forming a Vpas.saeewair 'it of annular cross-.saction between theftubefand the shell. l

When the heater in ,operation,thecombi1s tion takes place mainly in the combustion acharne ber but .combustion continues :for a time as the mixture "flows through the ,passageway 7:9- MQW ever, it will have Vbeen :combletduhy 'fthe `.time 'the gases reach .the exhaust end ofthe flSfSSlgeway 71E.

i this fact that the `pressure near V4the ofthe combustion chamber will be relatively low.. a her.- tain proportion of the 4'products .-,ofi ombustion will return from the exhaust 'end f to the combustion :chamber end-,through the ,reT turn tube 6. Theproducts ,of zcmbiistid admixed with the burning mixture will have the effect of maintaining uniform complete combustion, and since the products of combustion are cooler than the burning mixture flowing from the combustion chamber, the temperature of the gases flowing through the passageway 10 will be lowered. Such admixture of the products of combustion to the burning mixture will also result in some reduction in the temperature of the exhaust gases flowing through the exhaust pipe E4.

The invention is illustrated in Fig. 2 as applied to a heater having a spiral flow heat exchanger. A heat exchanger of this type is disclosed in the patent of William C. Parrish, No. 2,432,929.v

\ elongated port formed at oneside of the shell 16 and through a spiral passageway 82 formed by a plurality of spirally shaped sheets 84, "and ll.

The sides of the passageway 82 are closed by spiral header plates 88 and 89 while the plates 84- and 85 provide a passageway 90 which is generally spiral in cross section, the outer end of the passageway lEll) being `.formed between the sheet 86 and the casngtllll.` "The products of combustion are discharged through an exhaust conduit 92 which is connected to the outermost turn of the spiral passageway 82.

Within the shell 16 is a return pipe 94 suitably spaced from the shell to provide a passageway 96 for the flow of the products of combustion from the combustion chamber to the port 80.

As in the embodiment of 'the invention shown in Fig. 1, a portion of the products of combustion are returned to the burning mixture as it leaves the combustion chamber, such returned products of combustion serving to insure complete combustion of the fuel and lowering the temperature at which the products-.of combustion are discharged intothespiral passageway 82.

While particular embodimentsof the invention have been disclosed herein, it will be apparent to those skilled in the art that numerous additional Variations and modifications may be made Without departing from the more fundamental principles of the invention. It is therefore intended by the following claims to include Within thes'cope of the invention all such variations and modications by which substantially the results of the invention are obtained by the use of substantially the same or equivalent means.

The invention claimed is; 1.- A heater of the sealed combustion type comprising a.l casing, means forming a .cylindrical combustion chamber mounted within said casing, a heat exchanger having its inlet end connected to said combustion chamber to receive the burning mixture therefrom and` an outlet, said heat exchanger having a relatively large cylindrical compartment, means for vsupplying a combustible mixture to said combustion chamber including an induction pipe for the mixture having an outlet end extending along the inner cylindrical wall of said combustion chamber at the end of said chamber opposite the inlet to said heat exchanger in a tangential direction to cause helical ilow a central tube having its outlet end facing said combustion chamber for conducting a portion of the products of combustion from within said compartment to the reduced pressure space in the combustion chamber for admixture with the burning mixture therein, said tube being arranged so that its inlet end is located at a point within said compartment where the combustible mixture has ceased burning.

2. A heater of the sealed combustion type comprising a casing, means forming a cylindrical combustion chamber mounted within said casing, a heat exchanger having its inlet end connected to said combustion chamber to receive the burning mixture therefrom, and an exhaust end, said heat exchanger including a relatively elongated cylindrical chamber forming an axial extension on said combustion chamber, means for supplying a combustible mixture to said combustion chamber including an induction pipe having an outlet end extending along the inner cylindrical Wallof said combustion chamber at the end .of said chamber opposite the inlet to said heat exchanger in a tangential direction to cause a helical iiow of mixture within the combustion chamber, thereby creating an area of reduced pressure at the center of the combustion chamber, and a return tube extending axially in said elongated cylindrical chamber for conducting a portion of the products of combustion flowing therethrough from adjacent the exhaust end of the heat exchangerto the area of reduced pressure in said combustion chamber. y

THELMA MCCOLLUM, Eecutri of the Last Will .and Testament of Henry J. De N. M cCollu'm, Deceased.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS l Date l Faulds v Apr. 16, 1940 

